The stars in Hollywood are never the writers. Mainstream US cinema does not lose much sleep over scripts and, going by all the High School Musicals and comic book adaptations, it cannot be bothered to chase sentient beings much older than 30. Which makes Tony Gilroy something of a west coast Don Quixote. A screenwriter who made his name adapting Stephen King's Dolores Claiborne, he only began directing a couple of years ago. His specialism is action thrillers - not a genre famed for its smartness, yet his Saturday-night fare is enjoyably taxing. His new film Duplicity has neither car chases nor sex scenes - but it does star Julia Roberts and Clive Owen as ex-CIA and MI6 agents now in corporate espionage. The gag is that cold war technology is now used by shampoo manufacturers, yet for Gilroy the joy of a joke lies in the telling. His favourite device is the reversal - a surprise, a narrative feint, anything the audience does not expect. The story thus becomes as hard to grasp as cigarette smoke. The same dialogue is used five times, each time propelling the story in a new direction ("I hope the audience thinks the film is broken," Gilroy told the New Yorker). Gilroy swims in the mainstream, but uses arthouse tricks. His films should be stupid, yet turn out to be slyly clever. The mix is not to everyone's tastes. Steven Spielberg joked that the Duplicity DVD should include a bonus track, giving a straightforward rendition of the story. In line to direct the film, he ultimately dropped out.